This invention relates to a process and an apparatus for cooking a food product with hot moist air.
More particularly, the present invention relates to the complete or partial cooking of a food product by jets of hot moist air directed onto the surface of the product to be treated. Installations in which thermal energy is transferred to a food product by circulation of hot moist air are known. In installations such as these, which are described for example in U.S. Pat. Nos. 4,831,238, 4,474,498 and 4,154,861, hot moist air is brought into contact with the upper and lower faces of a grill-type conveyor on which the products to be cooked are arranged, the products travelling on the grill-type conveyor into an oven comprising means for circulating the hot moist air on either side of the grill.
These circulation means are formed by one or more fans which are positioned laterally and at the top or bottom of the oven and which are connected to branch circuits dividing the flow of hot moist air established into a descending vertical stream and an ascending vertical stream on either side of the grill-type conveyor.
The product to be treated thus moves perpendicularly to the descending vertical stream and ascending vertical stream of hot moist air.
Arrangements of this type have major inadequacies which always make them difficult or impossible to use, depending on the product to be treated.
Firstly, the need to branch the flow of hot moist air combined with the upper and lower circulation of the flows on either side of the grill-type conveyor creates maintenance problems, particularly in that part of the installation situated below the grill-type conveyor where the ascending vertical circulation of the air flow takes place.
This is because the juices produced by the complete or partial cooking of the products inevitably drop into the lower part of the installation which therefore has to be periodically dismantled, the false floor provided, more particularly in U.S. Pat. No. 4,831,238, failing to prevent the cooking juices from accumulating on the walls of the lower hot moist air circuit situated between the grill-type conveyor and the false floor.
In addition and as specifically described in U.S. Pat. Nos. 4,368,664 and 4,338,911, which relate to another two variants of the installations described above, the combination of an upper, descending vertical circulation and a lower, descending vertical circulation means that the flows of hot moist air do not pass through the bed formed by the materials to be treated and the grill-type conveyor but, on the contrary, are deflected by that bed.
Accordingly, this reduces the circulation of the hot air flow on the lateral faces so that these zones are poorly cooked.
Thus and although two flows of hot moist air are provided on either side of the grill-type conveyor, the products to be treated still have to be moved by being turned over during the cooking process so that the lateral faces can be cooked.
Finally, the heating of the grill-type conveyor inevitably caused by the lower ascending vertical flux automatically produces an increase in the temperature of the conveyor which in turn is accompanied by adhesion, sticking and, occasionally, calcination of the product to be treated.